text: The affinity of metal ions for ligands is described by a stability constant, also called the formation constant, and is represented by the symbol K. It is the equilibrium constant for its assembly from the constituent metal and ligands, and can be calculated accordingly, as in the following example for a simple case:
  :xM  + yL   zZ 
  where : x, y, and z are the stoichiometric coefficients of each species. M stands for metal / metal ion , the L for Lewis bases , and finally Z for complex ions. Formation constants vary widely.  Large values indicate that the metal has high affinity for the ligand, provided the system is at equilibrium.
  Sometimes the stability constant will be in a different form known as the constant of destability. This constant is expressed as the inverse of the constant of formation and is denoted as K = 1/K . This constant represents the reverse reaction for the decomposition of a complex ion into its individual metal and ligand components. When comparing the values for K, the larger the value, the more unstable the complex ion is.
  As a result of these complex ions forming in solutions they also can play a key role in solubility of other compounds. When a complex ion is formed it can alter the concentrations of its components in the solution. For example:
  :Ag + 2NH  Ag(NH)
  :AgCl + HO  Ag + Cl
  If these reactions both occurred in the same reaction vessel, the solubility of the silver chloride would be increased by the presence of NHOH because formation of the Diammine argentum(I) complex consumes a significant portion of the free silver ions from the solution. By Le Chatelier's principle, this causes the equilibrium reaction for the dissolving of the silver chloride, which has silver ion as a product, to shift to the right.
  This new solubility can be calculated given the values of K and K for the original reactions. The solubility is found essentially by combining the two separate equilibria into one combined equilibrium reaction and this combined reaction is the one that determines the new solubility. So K, the new solubility constant, is denoted by: